<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Socket.IO chat</title>
  <style>
    * { margin: 0; padding: 0; box-sizing: border-box; }
    body { font: 13px Helvetica, Arial; }
    form { background: #000; padding: 3px; position: fixed; bottom: 0; width: 100%; }
    form input { border: 0; padding: 10px; width: 90%; margin-right: .5%; }
    form button { width: 9%; background: rgb(130, 224, 255); border: none; padding: 10px; }
    #messages { list-style-type: none; margin: 0; padding: 0; }
    #messages li { padding: 5px 10px; }
    #messages li:nth-child(odd) { background: #eee; }
  </style>
</head>
<body>
  <ul id="messages"></ul>
    <form action="">
      <input id="m" autocomplete="off" /><button>Send</button>
    </form>
  </ul>

  <script src="https://cdn.bootcss.com/socket.io/2.2.0/socket.io.js"></script>
  <script src="https://code.jquery.com/jquery-1.11.1.js"></script>

  <script>
    $(function () {
      var socket = io();//建立一个socket
      $('form').submit(function(){
        socket.emit('chat message', $('#m').val());//发送socket到服务器。
        $('#m').val('');
        return false;
      });
      socket.on('chat message', function(msg){
        console.log('--msg---', msg);
        $('#messages').append($('<li>').text(msg));
        window.scrollTo(0, document.body.scrollHeight);
        //接受服务器传回来的数据，新建一个li标签
      });
    });
  </script>
</body>
</html>